In that aspect of aesthetic dentistry which relates to self-administered use of in-home tooth whitening compositions, the dental patient is provided with a custom-fitted dental try having selectively enlarged tooth treating compartments which are adapted to receive a whitening gel that is dispensed from a syringe. The dental tray, with its gel content, is unobtrusively and advantageously worn by the patient at night and while the patient sleeps. This treatment is repeated for a sufficient period of time to effect the tooth bleaching and whitening process.
It is disclosed in the prior art that hydrogen peroxide, carbamide peroxide (urea peroxide) and other peroxides can be used as the whitening agents in the formulation of tooth whitening gels. The prior art also discloses that carboxypolymethylene (Carbopol) and poloxamer (Pluronic) as well as other thickeners can be used as the gelling agent in the preparation of peroxide gels. The gels can be water based or anhydrous.
U.S. Reissue Pat. No. 34,196 (Munro, 1993) discloses an anhydrous dental brightening gel comprising carbamide peroxide in a water-free gel for sustained release and which is applied to the teeth from a dental bleaching tray.
U.S. Pat. No. 5,631,000 (Pellico, 1997) discloses an anhydrous tooth whitening gel comprising carbamide peroxide dispersed in a substantially anhydrous gelatinous carrier containing, for example, neutralized carboxypolymethylene, hydroxypropyl cellulose, propylene glycol, polyethylene glycol and glycerin in an amount that does not exceed about 10 wt. % of the gel composition.
U.S. Pat. No. 5,098,303 (Fisher, 1992), U.S. Pat. No. 5,234,342 (Fisher, 1993), U.S. Pat. No. 5,376,006 (Fisher, 1994) and U.S. Pat. No. 5,409,631 (Fisher, 1995) disclose tooth bleaching and whitening gels formulated with carbamide peroxide, water, glycerin, carboxypolymethylene and sodium hydroxide wherein the concentration of carboxypolymethylene is so selected as to provide the gel composition with a tackiness or stickiness.
U.S. Pat. No. 5,401,495 (Murayama, 1992) discloses an aqueous dental bleaching gel comprising hydrogen peroxide, a gelling agent such as Carbopol (carboxypolymethylene), or polyoxyethylene polyoxypropylene block copolymers (poloxamer) as described in U.S. Pat. No. 3,639,574 (Schmolka, 1972), and a thickener identified as hydroxyethyl cellulose gum, hydroxypropyl cellulose gum, or carboxymethyl cellulose.
U.S. Pat. No. 5,425,953 (Sintov, et al., 1995) discloses a sustained-release, film forming, dental bleaching composition comprising a cellulosic polymer such as hydroxypropyl cellulose or carboxymethyl cellulose, a peroxy compound such as hydrogen peroxide, carbamide peroxide or sodium peroxyborate monohydrate, a stabilizing additive such as calcium disodium ededate, and a vehicle such as water, ethyl alcohol or a combination thereof.
U.S. Pat. No. 4,839,156 (Ng, et al., 1989), which is incorporated herein by reference, discloses a hydrogen peroxide dental gel containing hydrogen peroxide, polyethylene glycol humectant, a non-ionic surfactant such as Tween 20, flavoring and sweetening ingredients, and from about 18-25% by weight of polyoxyethylene polyoxypropylene block copolymer (Pluronic/Poloxamer) gelling agent.
U.S. Pat. No. 4,980,152 (Frazier, et al., 1990) discloses an aqueous dental gel comprising hydrogen peroxide or carbamide peroxide, a thickening agent such as Carbopol brand carboxypolymethylene in an amount from about 0.5 to about 6.5% by weight and/or a non-ionic surfactant such as Pluronic F127 brand poloxamer in an amount from about 10 to about 28% by weight, together with a fluoride, cellulosic thickener, buffering agent, glycerine, preservatives and water.
U.S. Pat. No. 5,059,417 (Williams, et al., 1991) discloses a clear dental gel containing a peroxygen compound such as sodium perborate, persilicate, perphosphate or hydrogen peroxide, poloxamer gelling agent and glycerol in an amount to stabilize the gel against low temperature liquification.
U.S. Pat. No. 4,528,180 (Schaeffer, 1985), U.S. Pat. No. 4,687,663 (Schaeffer, 1987) and U.S. Pat. No. 4,849,213 (Schaeffer, 1989) disclose a two-component dental product wherein a first component comprises a dental gel containing, for example, hydrogen peroxide, water, Carbopol 934, Pluronic F127, hydroxypropyl methyl cellulose and sodium hydroxide, and the second component comprises an aqueous dental paste containing, for example, sodium bicarbonate, sodium chloride, glycerin, propylene glycol, thickener and polishing agent. The first and second components are adapted to be simultaneously dispensed onto a toothbrush for application to the teeth. The patentee points out that the two-component system provides the oral care benefits achieved through the combination of hydrogen peroxide, sodium bicarbonate and table salt and overcomes the hydrogen peroxide dissociation that would arise through the unitary packaging of these ingredients, since hydrogen peroxide and sodium bicarbonate immediately react upon mixing.
Heretofore, dental bleaching gels adapted for use with dental bleaching trays have been formulated to provide for sustained release of the active bleaching agent over a period of several hours, including overnight use. The tray bleaching procedure typically specified that the bleaching step be repeated on a daily basis for up to about 14 days to achieve significant whitening. The long period of use required by the prior art tray bleaching procedure as well as tissue sensitivity and irritation associated with this extended procedure tends to diminish full compliance with the specified schedule for use of the bleaching gel. Accordingly, there is a need for a more rapidly acting dental bleaching gel which is adapted for use with dental bleaching trays and which reduces tissue sensitivity and irritation to thereby enhance compliance with the specified procedure for using the bleaching gels in order to achieve the most effective results.
It is disclosed in the prior art that the rate of dental bleaching with hydrogen peroxide, normally at pH 4.4, increases when the hydrogen peroxide is buffered to an alkaline pH. Howard Frysh, et al. (Journal of Esthetic Dentistry, Vol. 7, No. 3, pp. 130-133, 1995) undertook an in vitro study to determine whether alkaline peroxide solutions might be more effective in whitening teeth in a given period of time than the acidic peroxide usually employed. This study compared, for a given time interval, the bleaching effectiveness of a commercially available bleaching composition containing 35% hydrogen peroxide at pH 4.4 with a like composition buffered to pH 9.0 with an aqueous sodium hydroxide solution. The results of the study showed that, for a given time interval, alkaline hydrogen peroxide was more effective in whitening teeth than conventional acidic hydrogen peroxide by a color whitening factor in excess of 2 to 1 as measured by a Minolta Chroma Meter.